A liquid crystal display device is a main flat display technology in the current market. The display device requires a backlight as a light source to illuminate the liquid crystal display device. A conventional backlight module includes a backlight source formed by LED. A light emitted from the backlight source become a surface light source and emitting out through the backlight module. Through a light homogenization function of a diffusion sheet, the light is emitted out from the backlight module. After passing through a liquid crystal panel, the panel can display a required image for us. Currently, in the liquid crystal display device, a white LED is usually adopted as a backlight source. The most common white LED is an LED formed by a blue light emitting chip and a yellow YAG phosphor. When an LED adopting the yellow YAG phosphor matches with the liquid crystal panel, the color saturation is lower, and the color of the display device is not colorful enough.